Here's a number Italians should keep in mind next time they sign up for a fixed broadband plan: 5.1. It's the likely download speed their broadband connection will offer, no matter how many megabits their ISP's adverts feature.

5.1Mbps is the average download speed of Italy's ADSL connections according to a recent report by Italian price comparison website SOS Tariffe. Among the country's different regions, Tuscany and Liguria emerge as the fastest in broadband terms, with both seeing an average downlink speed of 5.6 Mbps, while Abruzzo and Veneto finish at the bottom of the table with 4.2Mbps and 4.1Mbps respectively.

The research results come as no surprise as Italy's connections have long been known to be sub-par. According to Akamai's most recent State of the Internet report, Italy's average broadband speed of 4.4Mbps puts the country 45th globally.

That means 'Il Belpaese' trails other European countries including UK (with 7.9 Mbps), Germany (6.9Mbps), Spain (5.2Mbps), France (5.2Mbps) and is a long way behind the likes of the Netherlands (9.9Mbps), Finland (7.7Mbps) and Norway (7.7Mbps).

"In Italy ADSL is by far the most common technology to access the internet, while in other countries cable or FTTx connections, which are usually faster, are more widespread," Alberto Mazzetti, cofounder of SOS Tariffe, said.

Italy's lower average broadband speeds might also be due to a low broadband penetration rate: "Speed and investments are higher where the demand is higher," Mazzetti said.

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According to Eurostat, the EU's statistics service, just 55 percent of Italian households have a broadband connection compared to an average of 72 percent across the EU, while 37 percent of Italians have never used the internet compared to 15 percent of the Germans and French and 10 percent of Brits.

SOS Tariffe's report — based on 500,000 tests performed through its measurement software — also shows there's a significant difference between actual and advertised ADSL speed in Italy.

For connections advertised with a 20Mbps top speed, real world speed came out at 7.2Mbps — that is, 64 percent slower that claimed — while 7Mbps speed deals, known as 7 Mega, delivered average speeds of 4Mbps (43 percent less).

"This is not a uniquely Italian problem because it is due to ADSL's own technical limitations," Mazzetti said. "The difference, again, is that abroad other more efficient fixed broadband technologies are more common."

The discrepancy between advertised and actual speed might however be narrower according to other speed test systems, such as the one set up by Italy’s telecoms regulator AgCom. In the case of the biggest ISPs, the average speed for a nominal 20Mbps connection stands at between 13Mbps and 15Mbps, AgCom found, while tariffs advertised at 7Mbps come in at between 6.4Mbps and 6.6Mbps.

That doesn’t mean though that Italian broadband customers can celebrate though. Most of the users testing their connection speed with AgCom’s software indeed find that their ISP doesn’t respect the minimum speed guaranteed by the contract. That happens between 60 percent to 87 percent of the times for the six biggest ISPs.

However, even this figure should be taken with a grain of salt: "Users who opt for our software are more likely to have problems with their connection," said Sergio Del Grosso, head of AgCom's QoS office. "They choose it over other tests because they want an official document to use in their complaints to their [internet service] provider."